Systems and methods for tracking a path using the null-space

ABSTRACT

Devices, systems, and methods for providing a desired movement of one or more joints of a manipulator arm having a plurality of joints with redundant degrees of freedom while effecting commanded movement of a distal end effector of the manipulator. Methods include defining a constraint, such as a network of paths, within a joint space defined by the one or more joints and determining a movement of the plurality of joints within a null-space to track the constraints with the one or more joints. Methods may further include calculating a reconfiguration movement of the joints and modifying the constraints to coincide with a reconfigured position of the one or more joints. Various configurations for devices and systems utilizing such methods are provided herein.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a Non-Provisional of and claims the benefit ofpriority from U.S. Provisional Patent Application No. 61/799,444 filedon Mar. 15, 2013 and entitled “Systems and Methods for Tracking a PathUsing the Null-Space”, the full disclosure of which is incorporatedherein by reference.

The present application is generally related to the followingcommonly-owned applications: U.S. application Ser. No. 12/494,695 filedJun. 30, 2009, entitled “Control of Medical Robotic System ManipulatorAbout Kinematic Singularities;” U.S. application Ser. No. 12/406,004filed Mar. 17, 2009, entitled “Master Controller Having RedundantDegrees of Freedom and Added Forces to Create Internal Motion;” U.S.application Ser. No. 11/133,423 filed May 19, 2005 (U.S. Pat. No.8,004,229), entitled “Software Center and Highly Configurable RoboticSystems for Surgery and Other Uses;” U.S. application Ser. No.10/957,077 filed Sep. 30, 2004 (U.S. Pat. No. 7,594,912), entitled“Offset Remote Center Manipulator For Robotic Surgery;” and U.S.application Ser. No. 09/398,507 filed Sep. 17, 1999 (U.S. Pat. No.6,714,839), entitled “Master Having Redundant Degrees of Freedom;” U.S.Provisional Application No. 61/654,755 filed Jun. 1, 2012, entitled“Manipulator Arm-to-Patient Collision Avoidance Using a Null-Space;” andU.S. Provisional Application No. 61/654,773 filed Jun. 1, 2012, entitled“System and Methods for Avoiding Collisions Between Manipulator ArmsUsing a Null-Space,” the disclosures of which are incorporated herein byreference in their entireties.

BACKGROUND OF THE INVENTION

The present invention generally provides improved surgical and/orrobotic devices, systems, and methods.

Minimally invasive medical techniques are aimed at reducing the amountof tissue which is damaged during diagnostic or surgical procedures,thereby reducing patient recovery time, discomfort, and deleterious sideeffects. Millions of “open” or traditional surgeries are performed eachyear in the United States; many of these surgeries can potentially beperformed in a minimally invasive manner. However, only a relativelysmall number of surgeries currently use minimally invasive techniquesdue to limitations in surgical instruments, and techniques, and theadditional surgical training required to master them.

Minimally invasive telesurgical systems for use in surgery are beingdeveloped to increase a surgeon's dexterity as well as to allow asurgeon to operate on a patient from a remote location. Telesurgery is ageneral term for surgical systems where the surgeon uses some form ofremote control, e.g., a servomechanism, or the like, to manipulatesurgical instrument movements rather than directly holding and movingthe instruments by hand. In such a telesurgery system, the surgeon isprovided with an image of the surgical site at the remote location.While viewing typically a three-dimensional image of the surgical siteon a suitable viewer or display, the surgeon performs the surgicalprocedures on the patient by manipulating master control input devices,which in turn control the motion of robotic instruments. The roboticsurgical instruments can be inserted through small, minimally invasivesurgical apertures to treat tissues at surgical sites within thepatient, often the trauma associated with accessing for open surgery.These robotic systems can move the working ends of the surgicalinstruments with sufficient dexterity to perform quite intricatesurgical tasks, often by pivoting shafts of the instruments at theminimally invasive aperture, sliding of the shaft axially through theaperture, rotating of the shaft within the aperture, and/or the like.

The servomechanism used for telesurgery will often accept input from twomaster controllers (one for each of the surgeon's hands) and may includetwo or more robotic arms or manipulators. Mapping of the hand movementsto the image of the robotic instruments displayed by the image capturedevice can help provide the surgeon with accurate control over theinstruments associated with each hand. In many surgical robotic systems,one or more additional robotic manipulator arms are included for movingan endoscope or other image capture device, additional surgicalinstruments, or the like.

A variety of structural arrangements can be used to support the surgicalinstrument at the surgical site during robotic surgery. The drivenlinkage or “slave” is often called a robotic surgical manipulator, andexemplary linkage arrangements for use as a robotic surgical manipulatorduring minimally invasive robotic surgery are described in U.S. Pat.Nos. 6,758,843; 6,246,200; and 5,800,423, the full disclosures of whichare incorporated herein by reference. These linkages often make use of aparallelogram arrangement to hold an instrument having a shaft. Such amanipulator structure can constrain movement of the instrument so thatthe instrument shaft pivots about a remote center of spherical rotationpositioned in space along the length of the rigid shaft. By aligningthis center of rotation with the incision point to the internal surgicalsite (for example, with a trocar or cannula at an abdominal wall duringlaparoscopic surgery), an end effector of the surgical instrument can bepositioned safely by moving the proximal end of the shaft using themanipulator linkage without imposing potentially dangerous forcesagainst the abdominal wall. Alternative manipulator structures aredescribed, for example, in U.S. Pat. Nos. 6,702,805; 6,676,669;5,855,583; 5,808,665; 5,445,166; and 5,184,601, the full disclosures ofwhich are incorporated herein by reference.

While the new robotic surgical systems and devices have proven highlyeffective and advantageous, still further improvements would bedesirable. For example, a manipulator arm may include additionalredundant joints to provide increased movements or configurations undercertain conditions. When moving surgical instruments within a minimallyinvasive surgical site, however, these joints may exhibit a significantamount of movement outside the patient, often more movement than neededor expected, particularly when pivoting instruments about minimallyinvasive apertures through large angular ranges. Alternative manipulatorstructures have been proposed which employ software control over ahighly configurable kinematic manipulator joint set to restrain pivotalmotion to the insertion site while inhibiting inadvertentmanipulator/manipulator contact outside the patient (or the like). Thesehighly configurable “software center” surgical manipulator systems mayprovide significant advantages, but may also present challenges. Inparticular, the mechanically constrained remote-center linkages may havesafety advantages in some conditions. Additionally, the wide range ofconfigurations of the numerous joints often included in thesemanipulators may result in the manipulators being difficult to manuallyset-up in a configuration that is desirable for a particular procedure.Nonetheless, as the range of surgeries being performed usingtelesurgical systems continues to expand, there is an increasing demandfor expanding the available configurations and the range of motion ofthe instruments within the patient. Unfortunately, both of these changescan increase the challenges associated with the motion of themanipulators outside the body, and can also increase the importance ofavoiding excessive movement of the manipulators arm for certain tasks.

For these and other reasons, it would be advantageous to provideimproved devices, systems, and methods for surgery, robotic surgery, andother robotic applications, and it would be particularly beneficial ifthese improved technologies provided the ability to provide moreconsistent and predictable movement of the manipulator arm duringcertain tasks. It would be further desirable to provide suchimprovements while increasing the range of motion of the instruments forat least some tasks and without significantly increasing the size,mechanical complexity, or costs of these systems, and while maintainingor improving their dexterity.

BRIEF SUMMARY OF THE INVENTION

The present invention generally provides improved robotic and/orsurgical devices, systems, and methods. In many embodiments, theinvention will employ highly configurable surgical robotic manipulators.These manipulators, for example, may have more degrees of freedom ofmovement than the associated surgical end effectors have within asurgical workspace. A robotic surgical system in accordance with thepresent invention typically includes a manipulator arm supporting arobotic surgical instrument and a processor to calculate coordinatedjoint movements for manipulating an end effector of the instrument. Thejoints of the robotic manipulators supporting the end effectors allowthe manipulator to move throughout a range of different configurationsfor a given end effector position and/or a given pivot point location.In one aspect, the invention provides improved consistency andpredictability of movement of the manipulator arm by defining a set ofconstraints or path segments along which movement is desired for one ormore joints of the manipulator arm.

In one aspect, the robotic surgical system may utilize holonomic orposition-based constraints that are defined within a joint-space orCartesian-coordinate space of the manipulator arm and correspond to adesired movement of one or more joints of a manipulator arm having adistal end effector. Virtual potential fields may be calculated and usedto determine movement of the one or more joints within a null-space sothat a position of the one or more joints moves toward the constraintsthereby providing the desired movement of the one or more joints whilemaintaining a desired position of an end effector. This approach allowsfor improved control over the movement of one or more joints within anull-space, particularly in a manipulator arm utilizing a Jacobian basedcontroller in which the primary calculations of the one or more jointsare based on velocities rather than positions.

In some embodiments, a manipulator arm may include additional redundantjoints to allow for various types of movement, such as a reconfigurationmovement in response to a user command or an external manualarticulation of a joint. In certain aspects, rather than relying onrobotic devices that are mechanically constrained to pivot a tool abouta fixed point in space, or robotic devices having passive joints whichpassively pivot about the tissues of a minimally invasive aperture, thepresent invention may calculate a motion that includes pivoting a linkof the manipulator linkage about an aperture site. The degrees offreedom of the robotic linkages supporting the end effectors can allowthe linkage to move throughout a range of configurations for a given endeffector position, and the systems may drive the linkages toconfigurations which inhibit collisions involving one or more movingrobotic structures. Set-up of highly flexible robotic linkages can befacilitated by processors which drive one or more joints of the linkagewhile the linkage is being manually positioned.

In some embodiments, the invention allows for movement of themanipulator arm to be directed towards a pre-determined set ofconstraints when moving to effect one or more tasks, such as a desiredend effector movement, a reconfiguration movement or various othersmovements. It should be noted that the manipulator arm need not bemechanically “locked” to the set of constraints, but rather theconstraints can be utilized to direct movement of one or more joints ofthe manipulator arm toward the constraints when moving according to oneor more commanded movements. In some embodiments, the manipulator armmay include various movements or modes of operation in which jointmovements of the manipulator arm are not limited by the definedconstraints.

In general, commanded movement of the manipulator arm to effect movementof the distal end effector utilizes movement of all the joints of themanipulator arm. Various other types of movement, such as a commandedreconfiguration movement or collision avoidance, may utilize the samejoints as used in manipulation of the end effector or may includevarious other selected joints or sets of joints. When effecting movementof the end effector a manipulator arm having redundant degrees offreedom, the motion of the joints according to one or more of thesetypes of movement may result in unnecessary, unpredictable, ornon-holonomic movement of the manipulator arm, since an unusednull-space indicates unspecified motion. In addition, movement of anupper portion of a manipulator arm may unnecessarily limit the availablerange of motion of an adjacent manipulator arm. To provide improvedmovement of the manipulator arms, the redundant degrees of freedom maybe used to adhere to a set of constraints to limit motion of themanipulator arm within or direct movement toward a repeatable pattern ofmovement. In some embodiments, the repeatable pattern of movement isbased on pre-determined positions or a range of positions of themanipulator arm. In certain aspects, the constraints may be defined ineither the joint-space using joint velocities or within theCartesian-coordinate space using positions.

In one aspect, the movement of a manipulator arm having redundantdegrees of freedom utilizes primary calculations based on jointvelocities, such as by using a Jacobian based controller. The system maydefine a set of holonomic or position based constraints, such as a pathor network of paths, in either the joint-space or theCartesian-coordinate space. The constraints may be used to develop anartificial potential field to “pull” or direct the movement of themanipulator arm towards the constraints using movement of the jointswithin a null-space of the Jacobian. This allows the one or more jointsof the manipulator arm to move according to the desired pattern ofmovement corresponding to the constraints, while maintaining a desiredstate of the end effector during commanded end effector movements.

In some embodiments, the invention provides a robotic system comprisinga manipulator assembly for robotically moving a distal end effectorrelative to a proximal base. The manipulator assembly has a plurality ofjoints, the joints providing sufficient degrees of freedom to allow arange of joint states for an end effector state. An input receives acommand to effect a desired movement of the end effector. A processorcouples the input to the manipulator assembly. The processor has a firstmodule and a second module. The first module is configured to helpcalculate movements of the joints in response to the command so as tomove the end effector with the desired movement. The second module isconfigured to help drive at least one of the joints in response to anexternal articulation of another joint of the manipulator assembly.

In certain aspects, the first and second modules of the processor willbe used differently in different control modes. For example, theprocessor may have first and second modes. The first mode will oftencomprise a mode for tracking the network of paths for the end effectorin its Cartesian space, while the second mode may comprise a clutchmode. In the first mode, the tool tip responds to the surgeon's positionand orientation commands. While in the clutch mode, in response to amanual articulation of a joint, at least one other joint is driven bythe processor so that the combined movement of the joints in this secondmode is within a null-space of the Jacobian. This can provide themanipulator assembly with an effective clutch degree of freedom whichdiffers from a degree of freedom of the driven clutch joint, and from adegree of freedom of the other joint. For example, a manipulatorassembly providing the end effector with six mechanical degrees offreedom could be constrained so as to allow the end effector to be movedin space solely about a pivotal rotation center located where no jointis present. Alternatively, such an end effector might be translatablealong an arbitrary plane which is at a skew angle relative to everylinkage and joint axis of the manipulator linkage assembly. To providethese and/or other capabilities, the driven clutch mode will oftencomprise a plurality of driven clutch joints, and the processor will beconfigured to drive each driven clutch joint in response to manualmanipulation of a plurality of joints of the manipulator assembly sothat the manipulator assembly has a plurality of effective clutchdegrees of freedom when the processor is in the clutch mode.

The manipulator assembly will often comprise a surgical tool orinstrument having a shaft extending between a mounting interface and theend effector. The processor in the first mode may be configured toderive the desired movement of the end effector within an internalsurgical space so that the shaft passes through a minimally invasiveaperture site. Such a master/slave controller may, for example, comprisea velocity controller using an inverse Jacobian matrix, which will oftencomprise a portion of the first module. The second module may be used inthe second or clutch mode, providing joint velocities along theJacobian's null-space to provide combinations of joint velocities thatare allowed in the clutch mode. The processor in the clutch mode isconfigured to allow manual articulation of the other joint (and often ofa plurality of joints of the manipulator system) while constrainingmotion of the end effector or some other structure of the manipulatorassembly which is disposed distally of the manually articulated and/orclutch driven joints. For example, manipulator assemblies having morethan six degrees of freedom may allow a user to push an intermediatelinkage of the manipulator assembly from a first location to a secondlocation while maintaining the end effector location in the workspace.This can result in a manipulator assembly having a pose which ismanually reconfigurable while the base and end effector remain fixed inspace. In some embodiments, an orientation of the end effector (or someother structure of the manipulator) may be orientationally constrainedby driving of the driven clutch joints while that structure is manuallytranslated to a new location.

In another aspect, movement of the arm may be calculated in accordancewith the constraints to effect movement along the desired path in afirst mode, such as a commanded end effector manipulation mode, whilethe movement of the arm while in a clutch mode or during a commandedreconfiguration movement is not similarly constrained. After theposition of the manipulator arm is reconfigured in the clutch mode or byeffecting a commanded reconfiguration within a null-space, the systemmay modify the constraints so as to translate or alter a position ororientation of the constraints to coincide with the reconfiguredlocation of the manipulator arm, or alternatively may select aconstraint from a set of constraints nearest the reconfigured location.

In one aspect of the present invention, a redundant degrees of freedom(RDOF) surgical robotic system with manipulate input is provided. TheRDOF surgical robotic system comprises a manipulator assembly, one ormore user input devices, and a processor with a controller. Amanipulator arm of the assembly has a plurality of joints providingsufficient degrees of freedom that allow a range of joint states for agiven end effector state. In response to a received reconfigurationcommand entered by a user, the system calculates velocities of theplurality of joints within a null-space. The joints are driven accordingto the reconfiguration command and the calculated movement so as tomaintain the desired state of the end effector. Typically, in responseto receiving a manipulation command to move the end effector with adesired movement, the system calculates end effector displacing movementof the joints by calculating joint velocities within anull-perpendicular-space of the Jacobian orthogonal to the null-space,and drives the joints according to the calculated movement to effect thedesired end effector movement. To provide increased range of motion forthe various other types of movements described above, the system mayinclude a revolute proximal most joint that affects the pitch of adistal instrument shaft of the manipulator and/or a distal revolutejoint coupling an instrument to a proximal portion of the manipulatorarm that effects a pivotal movement of the instrument shaft. Thesejoints may be utilized in any of the embodiments described herein.

In another aspect, the manipulator is configured to move such that anintermediate portion of the instrument shaft pivots about a remotecenter. Between the manipulator and the instrument, there are aplurality of driven joints providing sufficient degrees of freedom toallow a range of joint states for an end effector position when theintermediate portion of the instrument shaft passes through an accesssite. A processor having a controller couples the input device to themanipulator. In response to a reconfiguration command, the processordetermines movements of one or more joints to effect the desiredreconfiguration so that the intermediate portion of the instrument iswithin the access site during the end effector's desired movement andmaintains the desired remote center location about which the shaftpivots. Typically, in response to receiving a manipulation command toeffect a desired end effector's movement, the system calculates endeffector displacing movement of the joints, comprising calculating jointvelocities within a null-perpendicular-space of the Jacobian orthogonalto the null-space, and drives the joints according to the calculatedmovement to effect the desired end effector movement in which theinstrument shaft pivots about the remote center.

In another aspect, a joint from the first set of joints of themanipulator is a revolute joint coupling the manipulator arm to thebase. The desired state of the end effector may include a desiredposition, velocity or acceleration of the end effector. The manipulationcommand and the reconfiguration command may be separate inputs,typically being received from separate users on separate input devices,or may be separate inputs are received from the same user. In someembodiments, the end effector manipulation command is received from aninput device by a first user, such as a surgeon entering the command ona surgical console master input, while the reconfiguration command isreceived from an input device by a second user on a separate inputdevice, such as a physician's assistant entering the reconfigurationcommand on a patient side cart input device. In other embodiments, theend effector manipulation command and the reconfiguration command areboth received by the same user from input devices at a surgical console.

In yet another aspect of the present invention, a surgical roboticmanipulator with a proximal revolute joint and a distal parallelogramlinkage is provided, the pivotal axis of the revolute jointsubstantially intersecting with the axis of the instrument shaft of theend effector, preferably at a remote center if applicable. The systemfurther includes a processor having a controller coupling the input tothe manipulator arm and configured to calculate a movement of theplurality of joints in response to a user input command. The system mayinclude an input device for receiving a reconfiguration command to movea first set of joints of the plurality of joints with a desiredreconfiguration movement within the null-space or may include a clutchmode that allows a user to manually reconfigure one or more joints ofthe manipulator arm within the null-space as to maintain the endeffector the desired state. The system may be configured to adjust ortranslate the positional constraints in response to a user drivenreconfiguration or a manual reconfiguration of the manipulator arm, suchas in a clutch mode, to allow for improved consistency andpredictability of one or more joints within the null-space, whilemaintaining the desired state of the end effector, while providing theadditional capability of a user input or manual reconfiguration.

A further understanding of the nature and advantages of the presentinvention will become apparent by reference to the remaining portions ofthe specification and drawings. It is to be understood, however, thateach of the figures is provided for the purpose of illustration only andis not intended as a definition of the limits of the scope of theinvention. Furthermore, it is appreciated than any of the features inany of the described embodiments could be modified and combined with anyof various other features described herein or known to one of skill inthe art and still remain within the spirit and scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is an overhead view of a robotic surgical system in accordancewith embodiments of the present invention, the robotic surgical systemhaving a surgical station with a plurality of robotic manipulators forrobotically moving surgical instruments having surgical end effectors atan internal surgical site within a patient, in accordance with aspectsof the invention.

FIG. 1B diagrammatically illustrates the robotic surgical system of FIG.1A.

FIG. 2 is a perspective view illustrating a master surgeon console orworkstation for inputting surgical procedure commands in the surgicalsystem of FIG. 1A, the console including a processor for generatingmanipulator command signals in response to the input commands.

FIG. 3 is a perspective view of the electronics cart of FIG. 1A.

FIG. 4 is a perspective view of a patient side cart having fourmanipulator arms.

FIGS. 5A-5D show an exemplary manipulator arm.

FIGS. 6A-6B show an exemplary manipulator arm in the pitch forwardconfiguration and pitch back configurations, respectively.

FIG. 6C shows a graphical representation of the range of motion of thesurgical instrument tool tip of an exemplary manipulator arm, includinga cone of silence or conical tool access limit zone in each of the pitchforward and pitch back configurations.

FIG. 7A shows exemplary manipulator arms having a proximal revolutejoint that revolves the manipulator arm about an axis of a proximalrevolute joint.

FIG. 7B shows an exemplary manipulator arm and the associated range ofmotion and cone of silence, the exemplary manipulator arm having aproximal revolute joint that revolves the manipulator arm around an axisof a proximal revolute joint the movement of which can be used tomitigate the depicted cone of silence.

FIGS. 8A-8B show an exemplary manipulator arms having a revolute jointnear the distal instrument holder.

FIG. 9A schematically illustrates a highly flexible manipulator assemblyhaving a clutch input switch so as to facilitate manual positioning of asurgical tool adjacent a minimally invasive aperture while a processorconfigures the manipulator joint in response to the manual movement.

FIGS. 9B and 9C schematically illustrate reconfiguring of the joints ofthe manipulator assembly within a range of alternative jointconfigurations during manual movement of the arm.

FIGS. 10A-10C show sequential views of an exemplary manipulator armhaving a revolute joint near a distal instrument holder as the joint ismoved throughout its range of joint movement.

FIGS. 11A-11B show the revolved profile of an exemplary manipulator armhaving a distal revolute joint when the angular displacement of thejoint is 0° versus an angular displacement of 90°, respectively, inaccordance with aspects of the invention.

FIGS. 12A-12C show exemplary manipulator arms having a proximal jointthat translates a proximal joint supporting the manipulator arm about acurved path, in accordance with aspects of the invention.

FIGS. 13A-13B graphically represent the relationship between thenull-space and the null-perpendicular-space of the Jacobian of anexample manipulator assembly, in accordance with aspects of theinvention.

FIG. 13C graphically illustrates aspects of the null-clutch ornull-space clutch feature in regard to Cart-space commands, inaccordance with aspects of the invention.

FIG. 14A graphically illustrates an example of network path segments foruse in controlling movement of a manipulator assembly within thenull-space, in accordance with aspects of the invention.

FIG. 14B graphically illustrates an example of network path segments foruse in controlling movement of a manipulator assembly within thenull-space, in accordance with aspects of the invention.

FIGS. 15-16 schematically illustrate methods in accordance with aspectsof the invention.

FIGS. 17-18 illustrate example methods in accordance with aspects of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention generally provides improved surgical and roboticdevices, systems, and methods. The invention is particularlyadvantageous for use with surgical robotic systems in which a pluralityof surgical tools or instruments may be mounted on and moved by anassociated plurality of robotic manipulators during a surgicalprocedure. The robotic systems will often comprise telerobotic,telesurgical, and/or telepresence systems that include processorsconfigured as master-slave controllers. By providing robotic systemsemploying processors appropriately configured to move manipulatorassemblies with articulated linkages having relatively large numbers ofdegrees of freedom, the motion of the linkages can be tailored for workthrough a minimally invasive access site. The large number of degrees offreedom allows a system operator, or an assistant, to reconfigure thelinkages of the manipulator assemblies while maintaining the desired endeffector state, optionally in preparation for surgery and/or whileanother use maneuvers the end effector during a surgical procedure.While aspects of the invention are generally described manipulatorshaving redundant degrees of freedom, it is appreciated that aspects mayapply to non-redundant manipulators, for example a manipulatorexperiencing or approaching a singularity.

The robotic manipulator assemblies described herein will often include arobotic manipulator and a tool mounted thereon (the tool oftencomprising a surgical instrument in surgical versions), although theterm “robotic assembly” will also encompass the manipulator without thetool mounted thereon. The term “tool” encompasses both general orindustrial robotic tools and specialized robotic surgical instruments,with these later structures often including an end effector which issuitable for manipulation of tissue, treatment of tissue, imaging oftissue, or the like. The tool/manipulator interface will often be aquick disconnect tool holder or coupling, allowing rapid removal andreplacement of the tool with an alternate tool. The manipulator assemblywill often have a base which is fixed in space during at least a portionof a robotic procedure, and the manipulator assembly may include anumber of degrees of freedom between the base and an end effector of thetool. Actuation of the end effector (such as opening or closing of thejaws of a gripping device, energizing an electrosurgical paddle, or thelike) will often be separate from, and in addition to, these manipulatorassembly degrees of freedom.

The end effector will typically move in the workspace with between twoand six degrees of freedom. As used herein, the term “position”encompasses both location and orientation. Hence, a change in a positionof an end effector (for example) may involve a translation of the endeffector from a first location to a second location, a rotation of theend effector from a first orientation to a second orientation, or acombination of both. When used for minimally invasive robotic surgery,movement of the manipulator assembly may be controlled by a processor ofthe system so that a shaft or intermediate portion of the tool orinstrument is constrained to a safe motion through a minimally invasivesurgical access site or other aperture. Such motion may include, forexample, axial insertion of the shaft through the aperture site into asurgical workspace, rotation of the shaft about its axis, and pivotalmotion of the shaft about a pivot point adjacent the access site.

Many of the exemplary manipulator assemblies described herein have moredegrees of freedom than are needed to position and move an end effectorwithin a surgical site. For example, a surgical end effector that can bepositioned with six degrees of freedom at an internal surgical sitethrough a minimally invasive aperture and may in some embodiments havenine degrees of freedom (six end effector degrees of freedom-three forlocation, and three for orientation-plus three degrees of freedom tocomply with the access site constraints), but will often have ten ormore degrees of freedom. Highly configurable manipulator assemblieshaving more degrees of freedom than are needed for a given end effectorposition can be described as having or providing sufficient degrees offreedom to allow a range of joint states for an end effector position ina workspace. For example, for a given end effector position, themanipulator assembly may occupy (and be driven between) any of a rangeof alternative manipulator linkage positions. Similarly, for a given endeffector velocity vector, the manipulator assembly may have a range ofdiffering joint movement speeds for the various joints of themanipulator assembly within the null-space of the Jacobian.

The invention provides robotic linkage structures which are particularlywell suited for surgical (and other) applications in which a wide rangeof motion is desired, and for which a limited dedicated volume isavailable due to the presence of other robotic linkages, surgicalpersonnel and equipment, and the like. The large range of motion andreduced volume needed for each robotic linkage may also provide greaterflexibility between the location of the robotic support structure andthe surgical or other workspace, thereby facilitating and speeding upsetup.

The term “state” of a joint or the like will often herein refer to thecontrol variables associated with the joint. For example, the state ofan angular joint can refer to the angle defined by that joint within itsrange of motion, and/or to the angular velocity of the joint. Similarly,the state of an axial or prismatic joint may refer to the joint's axialposition, and/or to its axial velocity. While many of the controllersdescribed herein comprise velocity controllers, they often also havesome position control aspects. Alternative embodiments may relyprimarily or entirely on position controllers, acceleration controllers,or the like. Many aspects of control system that can be used in suchdevices are more fully described in U.S. Pat. No. 6,699,177, the fulldisclosure of which is incorporated herein by reference. Hence, so longas the movements described are based on the associated calculations, thecalculations of movements of the joints and movements of an end effectordescribed herein may be performed using a position control algorithm, avelocity control algorithm, a combination of both, and/or the like.

In many embodiments, the tool of an exemplary manipulator arm pivotsabout a pivot point adjacent a minimally invasive aperture. In someembodiments, the system may utilize a hardware remote center, such asthe remote center kinematics described in U.S. Pat. No. 6,786,896, theentire contents of which are incorporated herein in its entirety. Suchsystems may utilize a double parallelogram linkage which constrains themovement of the linkages such that the shaft of the instrument supportedby the manipulator pivots about a remote center point. Alternativemechanically constrained remote center linkage systems are known and/ormay be developed in the future. Surprisingly, work in connection withvarious aspects of the invention indicates that remote center linkagesystems may benefit from highly configurable kinematic architectures. Inparticular when a surgical robotic system has a linkage that allowspivotal motion about two axes intersecting at or near a minimallyinvasive surgical access site, the spherical pivotal motion mayencompass the full extent of a desired range of motion within thepatient, but may still suffer from avoidable deficiencies (such as beingpoorly conditioned, being susceptible to arm-to-arm or arm-to-patientcontact outside the patient, and/or the like). At first, adding one ormore additional degrees of freedom that are also mechanicallyconstrained to pivotal motion at or near the access site may appear tooffer few or any improvements in the range of motion. Nonetheless, suchjoints can provide significant advantages by allowing the overall systemto be configured in or driven toward a collision-inhibiting pose, byfurther extending the range of motion for other surgical procedures, andthe like. In other embodiments, the system may utilize software toachieve a remote center, such as described in U.S. Pat. No. 8,004,229,the entire contents of which are incorporated herein by reference. In asystem having a software remote center, the processor calculatesmovement of the joints so as to pivot an intermediate portion of theinstrument shaft about a pivot point determined, as opposed to amechanical constraint. By having the capability to compute softwarepivot points, different modes characterized by the compliance orstiffness of the system can be selectively implemented. Moreparticularly, different system modes over a range of pivotpoints/centers (e.g., moveable pivot points, passive pivot points,fixed/rigid pivot point, soft pivot points) can be implemented asdesired.

Despite the many advantages of a robotic surgical system having multiplehighly configurable manipulators, since the manipulators include arelatively large number of joints and links between the base andinstrument, manual positioning of the links can be challenging andcomplicated. Even when the manipulator structure is balanced so as toavoid gravitational effects, attempting to align each of the joints inan appropriate arrangement or to reconfigure the manipulator as desiredcan be difficult, time consuming, and may involve significant trainingand/or skill. The challenges can be even greater when the links of themanipulator are not balanced about the joints, such that positioningsuch a highly configurable structures in an appropriate configurationbefore or during surgery can be a struggle due to the manipulator armlength and the passive and limp design in many surgical systems.

These issues can be addressed by allowing a user, such as a physician'sassistant, to quickly and easily reconfigure the manipulator arm, whileand maintaining the desired end effector state, optionally even duringmovement of the end effector during a surgical procedure. One or moreadditional joints may be included in the manipulator arm to increase therange of motion and configurations of the manipulator arm to enhancethis capability. While providing additional joints may provide increasedrange of motion for certain tasks, the large number of redundant jointsin the manipulator arm may cause various movements of the arm to beoverly complex for other tasks, such that the movements appearunpredictable or the amount of overall movements causes various otherclinical concerns

In some embodiments, calculated movement relating to various othertasks, such as an avoidance movement based on an autonomous algorithm,may overlay the tracking movement so that the one or more joints may bemoved to effect various other tasks, as needed. Examples of suchavoidance movement are described in U.S. Provisional Application No.61/654,755 filed Jun. 1, 2012, entitled “Manipulator Arm-to-PatientCollision Avoidance Using a Null-Space;” and U.S. ProvisionalApplication No. 61/654,773 filed Jun. 1, 2012, entitled “System andMethods for Avoiding Collisions Between Manipulator Arms Using aNull-Space,” the disclosures of which are incorporated herein byreference in their entireties. The calculated movement that overlays thetracking movement of the one or more joints, however, is not limited tothe autonomous movement and may include various other movements, such asa commanded reconfiguration movement or various other movements.

Embodiments of the invention may include a user input which isconfigured to take advantage of the degrees of freedom of a manipulatorstructure. Rather than manually reconfiguring the manipulator, the inputfacilitates use of driven joints of the kinematic linkage to reconfigurethe manipulator structure in response to entry of a reconfigurationcommand by a user. In many embodiments, the user input for receiving thereconfiguration command is incorporated into and/or disposed near themanipulator arm. In other embodiments, the input comprises a centralizedinput device to facilitate reconfiguration of one or more joints, suchas a cluster of buttons on the patient side cart or a joystick.Typically, the input device for receiving the reconfiguration command isseparate from the input for receiving a manipulation command to effectmovement of the end effector. A controller of the surgical system mayinclude a processor with readable memory having joint controllerprogramming instructions or code recorded thereon which allows theprocessor to derive suitable joint commands for driving the jointsrecorded thereon so as to allow the controller to effect the desiredreconfiguration in response to entry of the reconfiguration command. Itis appreciated, however, that the invention may be used in a manipulatorarms with or without a reconfiguration feature.

In the following description, various embodiments of the presentinvention will be described. For purposes of explanation, specificconfigurations and details are set forth in order to provide a thoroughunderstanding of the embodiments. However, it will also be apparent toone skilled in the art that the present invention may be practicedwithout the specific details. Furthermore, well-known features may beomitted or simplified in order not to obscure the embodiment beingdescribed.

Referring now to the drawings, in which like reference numeralsrepresent like parts throughout the several views, FIG. 1A is anoverhead view illustration of a Minimally Invasive Robotic Surgical(MIRS) system 10, in accordance with many embodiments, for use inperforming a minimally invasive diagnostic or surgical procedure on aPatient 12 who is lying down on an Operating table 14. The system caninclude a Surgeon's Console 16 for use by a Surgeon 18 during theprocedure. One or more Assistants 20 may also participate in theprocedure. The MIRS system 10 can further include a Patient Side Cart 22(surgical robot) and an Electronics Cart 24. The Patient Side Cart 22can manipulate at least one removably coupled tool assembly 26(hereinafter simply referred to as a “tool”) through a minimallyinvasive incision in the body of the Patient 12 while the Surgeon 18views the surgical site through the Console 16. An image of the surgicalsite can be obtained by an endoscope 28, such as a stereoscopicendoscope, which can be manipulated by the Patient Side Cart 22 so as toorient the endoscope 28. The Electronics Cart 24 can be used to processthe images of the surgical site for subsequent display to the Surgeon 18through the Surgeon's Console 16. The number of surgical tools 26 usedat one time will generally depend on the diagnostic or surgicalprocedure and the space constraints within the operating room amongother factors. If it is necessary to change one or more of the tools 26being used during a procedure, an Assistant 20 may remove the tool 26from the Patient Side Cart 22, and replace it with another tool 26 froma tray 30 in the operating room.

FIG. 1B diagrammatically illustrates a robotic surgery system 50 (suchas MIRS system 10 of FIG. 1A). As discussed above, a Surgeon's Console52 (such as Surgeon's Console 16 in FIG. 1A) can be used by a Surgeon tocontrol a Patient Side Cart (Surgical Robot) 54 (such as Patent SideCart 22 in FIG. 1A) during a minimally invasive procedure. The PatientSide Cart 54 can use an imaging device, such as a stereoscopicendoscope, to capture images of the procedure site and output thecaptured images to an Electronics Cart 56 (such as the Electronics Cart24 in FIG. 1A). As discussed above, the Electronics Cart 56 can processthe captured images in a variety of ways prior to any subsequentdisplay. For example, the Electronics Cart 56 can overlay the capturedimages with a virtual control interface prior to displaying the combinedimages to the Surgeon via the Surgeon's Console 52. The Patient SideCart 54 can output the captured images for processing outside theElectronics Cart 56. For example, the Patient Side Cart 54 can outputthe captured images to a processor 58, which can be used to process thecaptured images. The images can also be processed by a combination theElectronics Cart 56 and the processor 58, which can be coupled togetherso as to process the captured images jointly, sequentially, and/orcombinations thereof. One or more separate displays 60 can also becoupled with the processor 58 and/or the Electronics Cart 56 for localand/or remote display of images, such as images of the procedure site,or other related images.

FIG. 2 is a perspective view of the Surgeon's Console 16. The Surgeon'sConsole 16 includes a left eye display 32 and a right eye display 34 forpresenting the Surgeon 18 with a coordinated stereo view of the surgicalsite that enables depth perception. The Console 16 further includes oneor more input control devices 36, which in turn cause the Patient SideCart 22 (shown in FIG. 1A) to manipulate one or more tools. The inputcontrol devices 36 can provide the same degrees of freedom as theirassociated tools 26 (shown in FIG. 1A) so as to provide the Surgeon withtelepresence, or the perception that the input control devices 36 areintegral with the tools 26 so that the Surgeon has a strong sense ofdirectly controlling the tools 26. To this end, position, force, andtactile feedback sensors (not shown) may be employed to transmitposition, force, and tactile sensations from the tools 26 back to theSurgeon's hands through the input control devices 36.

The Surgeon's Console 16 is usually located in the same room as thepatient so that the Surgeon may directly monitor the procedure, bephysically present if necessary, and speak to an Assistant directlyrather than over the telephone or other communication medium. However,the Surgeon can be located in a different room, a completely differentbuilding, or other remote location from the Patient allowing for remotesurgical procedures.

FIG. 3 is a perspective view of the Electronics Cart 24. The ElectronicsCart 24 can be coupled with the endoscope 28 and can include a processorto process captured images for subsequent display, such as to a Surgeonon the Surgeon's Console, or on another suitable display located locallyand/or remotely. For example, where a stereoscopic endoscope is used,the Electronics Cart 24 can process the captured images so as to presentthe Surgeon with coordinated stereo images of the surgical site. Suchcoordination can include alignment between the opposing images and caninclude adjusting the stereo working distance of the stereoscopicendoscope. As another example, image processing can include the use ofpreviously determined camera calibration parameters so as to compensatefor imaging errors of the image capture device, such as opticalaberrations.

FIG. 4 shows a Patient Side Cart 22 having a plurality of manipulatorarms, each supporting a surgical instrument or tool 26 at a distal endof the manipulator arm. The Patient Side Cart 22 shown includes fourmanipulator arms 100 which can be used to support either a surgical tool26 or an imaging device 28, such as a stereoscopic endoscope used forthe capture of images of the site of the procedure. Manipulation isprovided by the robotic manipulator arms 100 having a number of roboticjoints. The imaging device 28 and the surgical tools 26 can bepositioned and manipulated through incisions in the patient so that akinematic remote center is maintained at the incision so as to minimizethe size of the incision. Images of the surgical site can include imagesof the distal ends of the surgical instruments or tools 26 when they arepositioned within the field-of-view of the imaging device 28.

Regarding surgical tool 26, a variety of alternative robotic surgicaltools or instruments of different types and differing end effectors maybe used, with the instruments of at least some of the manipulators beingremoved and replaced during a surgical procedure. Several of these endeffectors, including DeBakey Forceps, microforceps, Potts scissors, andclip applier include first and second end effector elements which pivotrelative to each other so as to define a pair of end effector jaws.Other end effectors, including scalpel and electrocautery probe have asingle end effector element. For instruments having end effector jaws,the jaws will often be actuated by squeezing the grip members of handle.Single end effector instruments may also be actuated by gripping of thegrip members, for example, so as to energize an electrocautery probe.

The elongate shaft of instrument 26 allow the end effectors and thedistal end of the shaft to be inserted distally into a surgical worksitethrough a minimally invasive aperture, often through an abdominal wallor the like. The surgical worksite may be insufflated, and movement ofthe end effectors within the patient will often be effected, at least inpart, by pivoting of the instrument 26 about the location at which theshaft passes through the minimally invasive aperture. In other words,manipulators 100 will move the proximal housing of the instrumentoutside the patient so that shaft extends through a minimally invasiveaperture location so as to help provide a desired movement of endeffector. Hence, manipulators 100 will often undergo significantmovement outside patient P during a surgical procedure.

Exemplary manipulator arms in accordance with many embodiments of thepresent invention can be understood with reference to FIGS. 5A-13C. Asdescribed above, a manipulator arm generally supports a distalinstrument or surgical tool and effects movements of the instrumentrelative to a base. As a number of different instruments havingdiffering end effectors may be sequentially mounted on each manipulatorduring a surgical procedure (typically with the help of a surgicalassistant), a distal instrument holder will preferably allow rapidremoval and replacement of the mounted instrument or tool. As can beunderstood with reference to FIG. 4, manipulators are proximally mountedto a base of the patient side cart. Typically, the manipulator armincludes a plurality of linkages and associated joints extending betweenthe base and the distal instrument holder. In one aspect, an exemplarymanipulator includes a plurality of joints having redundant degrees offreedom such that the joints of the manipulator arm can be driven into arange of differing configurations for a given end effector position.This may be the case for any of the embodiments of manipulator armsdisclosed herein.

In many embodiments, such as shown for example in FIG. 5A, an exemplarymanipulator arm includes a proximal revolute joint J1 that rotates abouta first joint axis so as to revolve the manipulator arm distal of thejoint about the joint axis. In some embodiments, revolute joint J1 ismounted directly to the base, while in other embodiments, joint J1 maybe mounted to one or more movable linkages or joints. The joints of themanipulator, in combination, have redundant degrees of freedom such thatthe joints of the manipulator arm can be driven into a range ofdiffering configurations for a given end effector position. For example,the manipulator arm of FIGS. 5A-5D may be maneuvered into differingconfigurations while the distal member 511 (such as a cannula throughwhich the tool 512 or instrument shaft extends) supported within theinstrument holder 510 maintains a particular state and may include agiven position or velocity of the end effector. Distal member 511 istypically a cannula through which the tool shaft 512 extends, and theinstrument holder 510 is typically a carriage (shown as a brick-likestructure that translates on a spar) to which the instrument attachesbefore extending through the cannula 511 into the body of the patientthrough the minimally invasive aperture.

Describing the individual links of manipulator arm 500 of FIGS. 5A-5Dalong with the axes of rotation of the joints connecting the links asillustrated in FIG. 5A-5D, a first link 504 extends distally from apivotal joint J2 which pivots about its joint axis and is coupled torevolute joint J1 which rotates about its joint axis. Many of theremainder of the joints can be identified by their associated rotationalaxes, as shown in FIG. 5A. For example, a distal end of first link 504is coupled to a proximal end of a second link 506 at a pivotal joint J3that pivots about its pivotal axis, and a proximal end of a third link508 is coupled to the distal end of the second link 506 at a pivotaljoint J4 that pivots about its axis, as shown. The distal end of thethird link 508 is coupled to instrument holder 510 at pivotal joint J5.Typically, the pivotal axes of each of joints J2, J3, J4, and J5 aresubstantially parallel and the linkages appear “stacked” when positionednext to one another, as shown in FIG. 5D, so as to provide a reducedwidth w of the manipulator arm and improve patient clearance duringmaneuvering of the manipulator assembly. In many embodiments, theinstrument holder also includes additional joints, such as a prismaticjoint J6 that facilitates axial movement of instrument 306 through theminimally invasive aperture and facilitates attachment of the instrumentholder to a cannula through which the instrument is slidably inserted.

The distal member or cannula 511 through which the tool 512 extends mayinclude additional degrees of freedom distal of instrument holder 510.Actuation of the degrees of freedom of the instrument will often bedriven by motors of the manipulator, and alternative embodiments mayseparate the instrument from the supporting manipulator structure at aquickly detachable instrument holder/instrument interface so that one ormore joints shown here as being on the instrument are instead on theinterface, or vice versa. In some embodiments, cannula 511 includes arotational joint J8 (not shown) near or proximal of the insertion pointof the tool tip or the pivot point PP, which generally is disposed atthe site of a minimally invasive aperture. A distal wrist of theinstrument allows pivotal motion of an end effector of surgical tool 512about instrument joints axes of one or more joints at the instrumentwrist. An angle between end effector jaw elements may be controlledindependently of the end effector location and orientation.

The range of motion of an exemplary manipulator assembly can beappreciated by referring to FIGS. 6A-6C. During a surgical procedure, anexemplary manipulator arm can be maneuvered into a pitch forwardconfiguration, as shown in FIG. 6A, or into a pitch back configuration,as shown in FIG. 6B, as needed to access particular patient tissueswithin a surgical workspace. A typical manipulator assembly includes anend effector that can pitch forwards and backwards about an axis by atleast ±60 degrees, preferably by about ±75 degrees, and can also yawabout an axis by ±80 degrees. Although this aspect allows for increasedmaneuverability of the end effector with the assembly, there may beconfigurations in which movement of the end effector may be limited,particularly when the manipulator arm is in the full pitch forward orfull pitch back configuration as in FIGS. 6A and 6B. In one embodiment,the manipulator arm has a Range of Motion (ROM) of (+/−75 deg) for theouter pitch, and (+/−300 degrees) for the outer yaw joints,respectively. In some embodiments, the ROM may be increased for theouter pitch to provide a ROM larger than (+/−90 deg) in which case the“cone of silence” could be made to disappear entirely, althoughgenerally the inner sphere associated with insertion limitations wouldremain. It is appreciated that various embodiments may be configured tohave increased or decreased ROM, that the above noted ROMs are providedfor illustrative purposed, and further that the invention is not limitedto the ROMs described herein.

FIG. 6C graphically represents the overall range of motion and workspaceof the tool tip of the exemplary manipulator of FIGS. 5A-5B. Althoughthe workspace is shown as hemisphere, it may also be represented as asphere depending on the range of motion and configuration of one or morerevolute joints of the manipulator, such as joint J1. As shown, thehemisphere in FIG. 6C includes a central, small spherical void as wellas two conical voids. The voids represent the areas in which movement ofthe tool tip may be impossible due to mechanical constraints orunfeasible due to extremely high joint velocities that make movement ofthe end effector difficult or slow. For these reasons, the conical voidare referred to as the “cone of silence.” In some embodiments, themanipulator arm may reach a singularity at a point within the cone.Since movement of the manipulator within or near the cone of silence maybe impaired, it can be difficult to move the manipulator arm away fromthe cone of silence without manually moving one or more links of themanipulator to reconfigure the linkages and joints of the manipulator,which often requires an alternative operating mode and delays thesurgical procedure.

Movement of the instrument shaft into or near these conical portionstypically occurs when the angle between distal linkages in themanipulator is relatively small. Such configurations can be avoided byreconfiguring the manipulator to increase the angles between linkages(so that the linkages are moved into a more orthogonal position relativeto each other). For example, in the configurations shown in FIGS. 6A and6B, when the angle between the distal most link and the instrumentholder (angle a) becomes relatively small movement of the manipulatormay become more difficult. Depending on the range of joint movements inthe remaining joints in various embodiments, when the angle betweencertain linkages decreases, movement of the manipulator may be inhibitedand in some cases, the manipulator arm may no longer be redundant. Amanipulator configuration in which the instrument shaft nears theseconical portions, or in which the angles between linkages are relativelylow is said to be “poorly conditioned” such that maneuverability anddexterity of the manipulator arm is limited. It is desirable that themanipulator be “well conditioned” so as to maintain dexterity and rangeof movement. In one aspect, the present invention allows a user to avoidmovement of the instrument shaft near the above described conicalportions by simply entering a command to reconfigure the manipulator asdesired, even during movement of the end effector in a surgicalprocedure. This aspect is particularly useful should the manipulator,for whatever reason, become “poorly conditioned.”

While the embodiments of the manipulator described above may be utilizedin the present invention, some embodiments may include additionaljoints, which may also be used to improve dexterity and the conditioningof the manipulator arm. For example, an exemplary manipulator mayinclude a revolute joint and/or linkage proximal of joint J1 which canbe used to revolve the manipulator arm of FIG. 5A, and its associatedcone of silence, about an axis of the revolute joint so as to reduce oreliminate the cone of silence. In another embodiment, the exemplarymanipulator may also include a distal pivotal joint that pivots theinstrument holder about an axis substantially perpendicular to joint J5,thereby offsetting the tool tip so as to further reduce the cone ofsilence and improve the range of movement of the surgical tool. In stillanother embodiment, a proximal joint of the manipulator arm, such as J1,may be movably mounted on the base, so as to move or shift the cone ofsilence as needed and improve the range of motion of the manipulatortool tip. The use and advantages of such additional joints can beunderstood by referring to FIGS. 7A-13C, which illustrate examples ofsuch joints, which may each be used independent of one another or usedin combination, in any of the exemplary manipulator arms describedherein.

FIGS. 7A-7B illustrate an additional redundant joint for use withexemplary manipulator arms—a first joint coupling a proximal portion ofthe manipulator arm to the base. The first joint is a proximal revolutejoint J1′ that revolves the manipulator arm about a joint axis of jointJ1′. The proximal revolute J1′ includes a link 501 that offsets joint J1from the proximal revolute J1′ by a pre-determined distance or angle.The link 501 can be a curved linkage, as shown in FIG. 7A, or a linearor angled linkage, as shown in FIG. 7B. Typically, the joint axis of thejoint J1′ is aligned with the remote center RC or insertion point of thetool tip, as shown in each of FIG. 7A. In an exemplary embodiment, thejoint axis of joint J1′ passes through the remote center, as does eachother revolute joint axis in the manipulator arm, to prevent motion atthe body wall and can therefore be moved during surgery. The axis ofjoint J1′ is coupled to a proximal portion of the arm so it can be usedto change the position and orientation of the back of the arm. Ingeneral, redundant axes, such as this, allow the instrument tip tofollow the surgeon's commands while simultaneously avoiding collisionswith other arms or patient anatomy. In one aspect, the proximal revoluteJ1′ is used solely to change the mounting angle of the manipulator withrespect to the floor. This angle is important in order to 1) avoidcollisions with external patient anatomy and 2) reach anatomy inside thebody. Typically, the angle a between the proximal link of themanipulator attached to the proximal revolute joint J1′ and the axis ofthe proximal revolute is about 15 degrees.

FIG. 7B illustrates the relationship of the proximal revolute joint J1′and its associated joint axis and the cone of silence in an exemplarymanipulator arm. The joint axis of the proximal revolute joint J1′ maypass through the cone of silence or may be completely outside of thecone of silence. By revolving the manipulator arm about the axis of theproximal revolute J1′, the cone of silence can be reduced (in anembodiment where the joint J1′ axis passes through the cone of silence),or can be effectively eliminated (in an embodiment where the proximalrevolute joint axis extends completely outside the cone of silence). Thedistance and angle of the link 501 determines the position of the jointJ1′ axis relative to the cone of silence.

FIGS. 8A-8B illustrates another type of redundant joint for use withexemplary manipulator arms, a distal revolute joint J7 coupling theinstrument holder 510 to a distal link of the manipulator arm 508. Thedistal revolute joint J7 allows the system to laterally pivot or twistthe instrument holder 510 about the joint axis, which typically passesthrough the remote center or insertion point. Ideally, the revolutejoint is located distally on the arm and is therefore particularly wellsuited to moving the orientation of the insertion axis. The addition ofthis redundant axis allows the manipulator to assume multiple positionsfor any single instrument tip position. In general, redundant axes, suchas this, allow the instrument tip to follow the surgeon's commands whilesimultaneously avoiding collisions with other arms or patient anatomy.Because the distal revolute joint J7 has the ability to move theinsertion axis closer to the yaw axis, it is able to increase the rangeof motion when the manipulator arm is in a pitch back position. Therelationship between the axis of the distal revolute joint J7, the yawaxis of J1 and the insertion axis of tool tip is shown in FIG. 9. FIGS.10A-10C show the sequential movement of joint J7 and how movement ofjoint J7 shifts the insertion axis of tool tip from side to side.

Referring now to FIG. 9A, another alternative manipulator assembly 520includes a manipulator linkage arm 522 for removably supporting asurgical tool 524. A clutch input 516 comprises an input button whichcan be actuated by a hand engaging a link 518 of the manipulator that isto be disposed adjacent to access site 514 during surgery. This allowsthe hand to both actuate the input and help maneuver the manipulatorinto the appropriate position for surgery. In some embodiments,additional clutch inputs may be mounted on various other links so as toallow manual articulation of a link on which the clutch input isdisposed. In many embodiments, the link 518 on which clutch input 516 iscoupled to a shaft of a removable tool by an axial insertion joint. Insome embodiments, the hand which actuates the clutch input 516 may becapable of repositioning the manipulator in the clutch mode withoutassistance from another hand. In other embodiments, repositioning of themanipulator may be facilitated by having a user position both a firsthand on the manipulator link 518 adjacent clutch input 516, and a secondhand at a distance from the clutch input, particularly when reorientingthe link to a desired axial insertion angle. While clutch input 516 isactuated by the hand, the system processor will drive joints ofmanipulator 520 in response to manual movement of link 518.

If the clutched degrees of freedom of the slave manipulator linkagecoincide with one or more joint degrees of freedom (that is, if somejoints are locked and some joints are free to move in the clutch mode),then clutching is direct: one simply turns off the controller for thosejoints that are free to move. However, it will often be advantageous toclutch joints in a dependent way, where motion of one joint is linked bythe controller to motion of at least one other joint so that they can bemanually articulated together as a single degree of freedom. This may beachieved by driving at least one joint of a robotic manipulator assemblyin response to external articulation of at least one other joint. Thecontroller can effect this motion, which will often be different thanany degree of freedom of the mechanical system, by defining any desiredarbitrary linear combination of rates that can be treated as a singledegree of freedom that the operator may manipulate, optionally whilesome or all of the other mechanical degrees of freedom remain locked.This general concept includes port clutching, instrument clutching,elbow clutching (in which an intermediate elbow is allowed to move, forexample, from an upward oriented apex configuration around to alaterally oriented apex configuration while movement at the end effectorremains inhibited), and other clutching modes.

Referring now to FIGS. 9A and 9B, manipulator assembly 502 may bereconfigured by the processor for any of a variety of differing reasons.For example, a joint 526 may be driven from a downward oriented apexconfiguration to an upward oriented apex configuration so as to inhibitcollisions with an adjacent arm, equipment, or personnel; to enhance arange of motion of the end effector 508; in response to physiologicalmovement of the patient such as patient breathing or the like; inresponse to repositioning of the patient, such as by reorienting asurgical table; and the like. Some, but not all, of these changes inconfiguration of the manipulator assembly may be in response to externalforces applied to the manipulator assembly, with the processor oftendriving a different joint of the manipulator than that which is beingacted upon by the external force. In other cases, the processor willreconfigure the manipulator assembly in response to calculationsperformed by the processor. In either case, the processor may vary froma simple master-slave controller so as to drive manipulator assembly inresponse to a signal so as to provide a preferred manipulator assemblyconfiguration. Such configuring of the manipulator assembly may occurduring master-slave end effector movements, during manual or otherrepositioning of the manipulator assembly, and/or at least in part adifferent time, such as after releasing a clutch input.

In some embodiments, movement of the arm may be calculated in accordancewith the constraints to effect movement along the desired path in afirst mode, such as a commanded end effector manipulation mode, whilethe movement of the arm when in the clutch mode is not similarlyconstrained. After the position of the manipulator arm is reconfiguredin the clutch mode, the system may modify the constraint so as totranslate or alter the desired path associated with the constraints tothe reconfigured location of the manipulator arm. For example, theconstraints may be modified to move the desired path to the nearestpoint on the reconfigured manipulator arm so that subsequent movement ofthe manipulator arm at its reconfigured location moves toward or alongthe altered path of movement.

In another aspect, any of the systems described herein may utilize auser input device to drive one or more joints and reconfigure one ormore joints of the manipulator arm within a null-space to effect adesired reconfiguration for a variety of reasons. In an embodimenthaving one or both of a user input for commanded reconfiguration or aclutch mode as described above, the system may utilize the constraintsdescribed above during movement to effect commanded manipulationmovement and suspend application of the constraints during areconfiguration movement or while in the clutch mode. When thereconfiguration movement is completed or the manipulator arm is switchedout of clutch mode, the system may modify the position-based constraintsaccording to the reconfigured location of the manipulator arm. In otherembodiments, the constraints may define multiple positional paths ofmovement such that the constraints associated with the closest pathwithin the Cartesian-coordinate space can be selected. These aspectsallow the system to provide the desired movement of the one or morejoints of the manipulator arm after being reconfigured, by a drivenreconfiguration or a manual reconfiguration while in a clutch mode.

One advantage of the distal revolute joint J7 is that it may reduce thepatient clearance cone, which is the swept volume of the distal portionof the manipulator arm proximal of the insertion point which must clearthe patient to avoid collision between the patient and the instrumentholder or distal linkages of the manipulator arm. FIG. 11A illustratesthe patient clearance cone of the proximal portion of the manipulatorarm while the angular displacement of the distal revolute joint remainsat 0°. FIG. 11B illustrates the reduced patient clearance cone of theproximal portion of the manipulator arm while the distal revolute jointis shown having an angular displacement of 90° about its axis. Thus, inprocedures having minimal patient clearance near the insertion point,use of the joint J7 in accordance with the present invention may provideadditional clearance while maintaining the remote center location or theposition of the end effector as desired.

FIGS. 12A-12C illustrate another type of redundant joint for use withexemplary manipulator arms, a proximal joint that translates or revolvesthe manipulator arm about an axis. In many embodiments, this proximaltranslatable joint translates a proximal joint of the manipulator, suchas joint J1 or J1′, along a path so as to reduce or eliminate the coneof silence by shifting or rotating the range of motion of themanipulator arm to provide for better conditioning and improvedmaneuverability of the manipulator arm. The translatable joint mayinclude a circular path, such as shown in joint J1″ in FIGS. 12A-12D, ormay include a semi-circular or arcuate path, such as shown in FIGS.13A-13C. Generally, the joint revolves the manipulator arm about an axisof the translatable joint that intersects with the remote center RCabout which the shaft of the tool 512 extending through cannula 511pivots. Although in the embodiment shown in FIGS. 12A-12C, the axis ofJ1″ is a vertical axis, it is appreciated that the axis of J1″ may behorizontal or various angles of inclination.

In exemplary embodiments, the manipulator arm 500 may include any or allof a proximal or distal revolute joint, a proximal translatable jointand a parallelogram configuration of the distal linkages. Use of any orall of these features provide additional redundant degrees of freedomand facilitate reconfiguration in accordance with the present inventionso as to provide for a better “conditioned” manipulator assembly byincreasing the angles between linkages thereby improving the dexterityand motion of the manipulator. The increased flexibility of thisexemplary manipulator can also be used to optimize the kinematics of themanipulator linkage so as to avoid joint limits, singularities, and thelike.

In an exemplary embodiment, the joint movements of the manipulator arecontrolled by driving one or more joints by a controller using motors ofthe system, the joints being driven according to coordinated and jointmovements calculated by a processor of the controller. Mathematically,the controller may perform at least some of the calculations of thejoint commands using vectors and/or matrices, some of which may haveelements corresponding to configurations or velocities of the joints.The range of alternative joint configurations available to the processormay be conceptualized as a joint space. The joint space may, forexample, have as many dimensions as the manipulator has degrees offreedom, and a particular configuration of the manipulator may representa particular point in the joint space, with each coordinatecorresponding to a joint state of an associated joint of themanipulator.

In an exemplary embodiment, the system includes a controller in which acommanded position and velocity of a feature in the work-space, denotedhere as its Cartesian space, are inputs. The feature may be any featureon or off the manipulator, which can be used as a control frame to bearticulated using control inputs. An example of a feature on themanipulator, used in many examples described herein, would be thetool-tip. Another example of a feature on the manipulator would be aphysical feature which is not on the tool-tip, but is a part of themanipulator, such as a pin or a painted pattern. An example of a featureoff the manipulator would be a reference point in empty space which isexactly a certain distance and angle away from the tool-tip. Anotherexample of a feature off the manipulator would be a target tissue whoseposition relative to the manipulator can be established. In all thesecases, the end effector is associated with an imaginary control framewhich is to be articulated using control inputs. However, in thefollowing, the “end effector” and the “tool tip” are used synonymously.Although generally, there is no closed form relationship which maps adesired Cartesian space end effector position to an equivalentjoint-space position, there is generally a closed form relationshipbetween the Cartesian space end effector and joint-space velocities. Thekinematic Jacobian is the matrix of partial derivatives of Cartesianspace position elements of the end effector with respect to joint spaceposition elements. In this way, the kinematic Jacobian captures thekinematic relationship between the end effector and the joints. In otherwords, the kinematic Jacobian captures the effect of joint motion on theend effector. The kinematic Jacobian (J) can be used to map joint-spacevelocities (dq/dt) to Cartesian space end effector velocities (dx/dt)using the relationship below:dx/dt=Jdq/dt

Thus, even when there is no closed-form mapping between input and outputpositions, mappings of the velocities can iteratively be used, such asin a Jacobian-based controller to implement a movement of themanipulator from a commanded user input, however a variety ofimplementations can be used. Although many embodiments include aJacobian-based controller, some implementations may use a variety ofcontrollers that may be configured to access the Jacobian of themanipulator arm to provide any of the features described herein.

One such implementation is described in simplified terms below. Thecommanded joint position is used to calculate the Jacobian (J). Duringeach time step (Δt) a Cartesian space velocity (dx/dt) is calculated toperform the desired move (dx_(des)/dt) and to correct for built updeviation (Δx) from the desired Cartesian space position. This Cartesianspace velocity is then converted into a joint-space velocity (dq/dt)using the pseudo-inverse of the Jacobian (J^(#)). The resultingjoint-space commanded velocity is then integrated to produce joint-spacecommanded position (q). These relationships are listed below:dx/dt=dx _(des) /dt+kΔx  (1)dq/dt=J ^(#) dx/dt  (2)q _(i) =q _(i-1) +dq/dtΔt  (3)

The pseudo-inverse of the Jacobian (J) directly maps the desired tooltip motion (and, in some cases, a remote center of pivotal tool motion)into the joint velocity space. If the manipulator being used has moreuseful joint axes than tool tip degrees of freedom (up to six), (andwhen a remote center of tool motion is in use, the manipulator shouldhave an additional 3 joint axes for the 3 degrees of freedom associatedwith location of the remote center), then the manipulator is said to beredundant. A redundant manipulator's Jacobian includes a “null-space”having a dimension of at least one. In this context, the “null-space” ofthe Jacobian (N(J)) is the space of joint velocities whichinstantaneously achieves no tool tip motion (and when a remote center isused, no movement of the pivotal point location); and “null-motion” isthe combination, trajectory or path of joint positions which alsoproduces no instantaneous movement of the tool tip and/or location ofthe remote center. Incorporating or injecting the calculated null-spacevelocities into the control system of the manipulator to achieve thedesired reconfiguration of the manipulator (including anyreconfigurations described herein) changes above equation (2) to thefollowing:dq/dt=dq _(perp) /dt+dq _(null) /dt  (4)dq _(perp) /dt=J ^(#) dx/dt  (5)dq _(null) /dt=(1−J ^(#) J)z=V _(n) V _(n) ^(T) z=V _(n)α  (6)

The joint velocity according to Equation (4) has two components: thefirst being the null-perpendicular-space component, the “purest” jointvelocity (shortest vector length) which produces the desired tool tipmotion (and when the remote center is used, the desired remote centermotion); and the second being the null-space component. Equations (2)and (5) show that without a null-space component, the same equation isachieved. Equation (6) starts with a traditional form for the null-spacecomponent on the left, and on the far right side, shows the form used inan exemplary system, wherein (V_(n)) is the set of orthonormal basisvectors for the null-space, and (α) are the coefficients for blendingthose basis vectors. In some embodiments, a is determined by controlparameters, variables or setting, such as by use of knobs or othercontrol means, to shape or control the motion within the null-space asdesired.

Alternatively, in certain aspects, an augmented Jacobian thatincorporates a potential function gradient and is applied to theCartesian Space end effector velocities may be used. The augmentation ofthe Jacobian calculates the joint velocities as desired. It isunderstood that in referring to calculating joint movements using theJacobian, such calculations may include the augmented Jacobian approach.In accordance with the augmented Jacobian approach, the followingequations may be used, although it is appreciated that column vectorsmay be used:dx/dt=J*dq/dty=h(q)dy/dt=∂h/∂q*dq/dt[dx/dt ^(T) dy/dt ^(T)]^(T) =[J ^(T) ∂h/∂q ^(T)]^(T) *dq/dtd(x;y)/dt=[J;h]*dq/dtdq/dt=[J;h′] ^(#) d(x;y)/dt

In one example, set y=h(q) the complex network of potential fieldfunctions. dy/dt=∂h/∂q*dq/dt. dy/dt and ∂h/∂q and dy/dt can be dictatedas desired based on the potential field functions, and the augmentedequation would produce the combined desired result of both driving theend effector and tracking the paths in joint space. In one aspect, theaugmented Jacobian incorporates a potential function gradient and isapplied to the Cartesian space end effector velocities, wherein theaugmentation of the Jacobian calculated the joint velocities as desired,to provide the advantageous features described herein.

FIG. 13A graphically illustrates the relationship between the null-spaceof the Jacobian and the null-perpendicular-space of the Jacobian. FIG.14A shows a two-dimensional schematic showing the null-space along thehorizontal axis, and the null-perpendicular-space along the verticalaxis, the two axes being orthogonal to one another. The diagonal vectorrepresents the sum of a velocity vector in the null-space and a velocityvector in the null-perpendicular-space, which is representative ofEquation (4) above. FIG. 13B graphically illustrates the relationshipbetween the null-space and the null-motion manifold within afour-dimensional joint space, shown as the “null-motion manifold.” Eacharrow (q1, q2, q3, and q4) representing a principal joint axis. Theclosed curve represents a null-motion manifold which is a set ofjoint-space positions which instantaneously achieves the same endeffector position. For a given point A on the curve, since thenull-space is a space of joint velocities which instantaneously produceno movement of the end effector, the null-space is parallel to thetangent of the null-motion manifold at point A. To further highlight andillustrate the null-space concepts described herein, FIG. 13Cgraphically illustrates aspects of the null-space clutch feature inregard to Cart-space commands, in accordance with aspects of theinvention. In regard to the null-clutch or null-space clutch feature,the concept is that a sensed joint motion is matched as closely aspossible by the joint commands, but only along the null-space.

FIG. 14A graphically illustrates the two-dimensional subspace of thejoint-space of an exemplary manipulator arm, in accordance with oneaspect of the present invention. The horizontal and vertical axesrepresent the movement of two joints having independent joint movement,movement of joint affecting a pitch of an instrument holder of themanipulator arm (horizontal axis) versus movement of a distal revolutejoint that pivots the instrument holder laterally from a plane throughwhich a proximal portion of the manipulator arm extends (vertical axis).The right-most point of the joint patch represents the maximum forwardpitch of the tool tip, while the left most points of the path representthe maximum backward pitch of the tool tip. In certain embodiments, themanipulator arm uses a parallelogram linkage in which joints J3, J4 andJ5 are configured with interrelated movement to maintain theparallelogram formed by joints J3, J4, J5 and pivot point PP (see forexample FIG. 5A). Due to this interrelated movement, the pitch of theinstrument shaft may be determined by the state of a pitch joint (e.g.J3). Movement of the pitch joint, such as by joint J3 in FIG. 5A,changes the pitch of the insertion axis from a pitch forward position(see FIG. 6A) to a pitch back position (see FIG. 6B). In various otherembodiments, the pitch joint may include one or more joints of amanipulator arm the movement of which determine the pitch of theinstrument shaft. Movement of the distal revolute joint, such as distalrevolute joint J7 (see FIG. 8A) supporting the instrument holder 510 andassociated cannula 511, pivots or twists the instrument shaft extendingthrough instrument holder 510 laterally relative to a plane throughwhich the portion of the manipulator proximal of joint J7 extends. Thesub-space of the manipulator joint space illustrates the range ofpossible combinations of joint states for the pitch joint, J3, and therevolute joint, J7. Although in this embodiment, the positionalconstraints are defined within a subspace of the joint space defined bythe pitch joint and the distal revolute joint described above, it isappreciated that the subspace may be defined by various other joints orby three or more joints.

In some embodiments, the positional constraints are defined by a networkof paths within the subspace; each network defining a positional pathalong which a user desires the manipulator arm to move corresponds topath segments extending through the subspace of the manipulator jointspace that illustrate the combination of states between the pitch jointand the revolute joint. In the example of FIG. 14A, the desiredpositional path of the manipulator arm is defined by threeone-dimensional path segments defined to be piecewise continuous,segments A, B and C connected at a common intersection. In this example,since the range of motion of the distal revolute joint J7 can pivot theinstrument holder laterally in either direction from the plane of theportion of the manipulator arm proximal joint J7, the desired path isdefined to include movement of the joint in either direction (as shownby segments A and B). In such an embodiment, the system may beconfigured to control a tracking movement of the manipulator arm so thatthe position of the one or more joints move toward the nearest point onthe desired path. For example, the revolute joint J7 could be made tomove along segment B, rather than segment A, if joint J7 was nearersegment B when the path tracking movement is effected.

In this embodiment, the desired path includes relative movement of thedistal revolute joint and pitch joint so that movement of the pitchjoint to an increased pitch back position corresponds to increasedrotational displacement of the revolute joint, and movement of the pitchjoint to a pitch forward position corresponds to minimal or zerodisplacement of the distal revolute joint. As the outer pitch joint ispitched back, the tool tip on the instrument shaft moves forward. If theouter pitch joint reaches its limit in the pitch-back position, forwardmovement of a tool tip on the end of the instrument shaft 512 can stillbe achieved by movement of the distal revolute joint J7. It may beuseful however, to initiate movement of the distal revolute joint, J7,as the outer pitch joint J3 approaches its limit in the pitch-backposition. Similarly, in the pitch-forward direction, which causes tooltip motion in the backwards direction, the most backward tool tippositioning can be obtained when the movement of the distal revolutejoint is minimal, which is at zero angular displacement of the distalrevolute joint. In addition, when the angular displacement of the distalrevolute joint is greater or less than zero, the cross-section of themanipulator arm appears larger such that the arm may be more susceptibleto collisions with adjacent arms; therefore, it is advantageous toconstrain the distal revolute joint using the positional constraintsdescribed herein so that the angular displacement of the distal revolutejoint is at zero unless movement is desired for the reasons noted above;hence, to provide this desired movement between the outer pitch jointand the distal revolute joints, the constraints are defined as threenetwork paths shown in FIG. 14A.

At any point in time, being on any of the network of path segmentscoincides with meeting a one-dimensional constraint requiring aone-dimensional null-space. This two-dimensional subspace of manipulatorjoint space can be used to direct the movement of the manipulator arm tothe desired positional path by creating an attractive potential fieldwhich tends to “pull” or direct the Position P of the joint statestoward or along the defined path segments, typically the nearest pathsegment or segments. The system may be configured so that the trackingmovement of the joints cause the specified joints to move along thedefined path segments or may use various magnitudes of attraction withinthe potential field to cause the joints to move toward the segment pathsso that general movement is closer to the desired path. In one approach,this is accomplished by generating a potential field in joint-space,such that high potentials represent longer distances between the X (e.g.the current or calculated manipulator joint position) and the positionalconstraint (e.g. the network of paths), and lower potentials representshorter distances. The null-space coefficients (α) are then calculatedto descend down the negative gradient of the potential field, to thegreatest extent possible. In some embodiments, a potential associatedwith each path (e.g. b′ and c′) are determined from a distance betweenthe calculated position of the one or more manipulator joints and thedefined paths. In response to the calculated attractive force of theartificial potential field on the current joint positions, the systemcalculates movement of one or more joints of the manipulator arm withinthe null-space.

While the constraints may be defined as three segments A, B and C withina subspace defined by a distal revolute joint and an outer pitch jointas shown in FIGS. 14A-14B, it is appreciated that the above notedadvantages are associated with the particular kinematics of a givenmanipulator arm. Thus, as the kinematics may differ between manipulatorarms, so may the desired joint movements and the configuration ofnetwork path segments differ between manipulator arms. For example,depending on the design of a manipulator arm, it may be useful to definethe subspace in which the positional constraints are defined by two ormore other joints of the manipulator arm. For example, assuming anN-dimensional null-space, a network of N-dimensional manifolds in anyM-dimensional subspace of the full P-dimensional joint space may bedefined, where N≦M≦P. In a first example, in a one or more dimensionalnull-space, a network of one-dimensional curves or line segments may bedefined in the entire joint space or in any subspace of therein.Attractive potentials or velocities may then be calculated and projectedonto the null-space to determine the tracking movement so that aposition of the one or more joints tracks the defined paths. In a secondexample, assuming a null-space of two or more dimensions, a network oftwo-dimensional surfaces may be defined in the entire joint space or inany subspace therein. Again, attractive potentials or velocities maythen be calculated and projected on the null-space as described above.In both examples, the approach causes the manipulator to follow thenetwork of paths to produce the desired movement. In a third example,assuming a null-space of one dimension, a network of two-dimensionalsurfaces could still be defined in the entire joint space or in asubspace thereof, however, mapping velocities or attractive potentialsonto the null-space may provide limited capability in following thenetwork surfaces, e.g. only a one-dimensional subset of the surfaces maybe followed.

FIG. 14B illustrates a method of determining a tracking movement of amanipulator arm along a desired path, similar to that described in FIG.14A, except that the path segments may be modified, such as bytranslating or shifting a position or orientation of the path segmentsin response to various calculated joint states or operating mode of themanipulator arm. For example, as described above, a manipulator arm mayinclude a clutch mode in which a user can manually reconfigure amanipulator arm by applying an external force to one or more joints ofthe manipulator arm or a reconfiguration input allowing a user to driveone or more joints to reconfigure a position or configuration of themanipulator arm as desired. After reconfiguration of the manipulator armis completed upon exiting the clutch mode, the path segmentscorresponding to the desired positional path may be modified to coincidewith the position of the one or more joints having been reconfigured bythe user, or alternatively reconfigured by an autonomous algorithm suchas a collision avoidance algorithm. This aspect allows the manipulatorarm to retain the advantages of reconfiguration capabilities whileproviding the desired movement of the one or more joints and anyadvantages associated with such desired movement (e.g. increased rangeof motion, increased predictability and consistency of movement,decreased likelihood of collision, etc.).

In other embodiments, the defined path may include a plurality ofdifferent networks of path segments, each network of path segmentscorresponding to a different position or range of positions of the oneor more joints. Thus, rather than modifying a particular network ofpaths when the manipulator arm is reconfigured into a differentposition, the system may select a particular network of paths nearestthe position of the manipulator arm.

In one aspect, the approach includes defining positional constraints,such as in a joint-space or in the Cartesian-coordinate space of thetool tip (or some other portion of the manipulator and may include aremote center, such as found in either a hardware or software centersystem). For a manipulator with n-DOF of redundancy (e.g. ann-dimensional null-space of up to n constraints can be satisfiedsimultaneously). For a case having one-dimensional constraints, this mayinclude a set of piece-wise continuous constraints. For example, anetwork of line segments or curves may be used to define a network ofpaths in either the joint-space of the Cartesian-coordinate space. Thenetwork of paths may be either static or may be dynamically redefinedduring the course of surgery. A static network path may be defined atstart-up or may be selected by a user or the system from a plurality ofstatic network paths, while a dynamic network path may be dynamicallyredefined by the system, or by a user, during the course of surgery.

Once the network of paths is determined, the movement of the joints ofthe manipulator arm is calculated so that the position of the one ormore joints tracks the paths so as to provide the desired movement ofthe one or more joints. In one aspect, the joints of the manipulator armtracks the network of path segments based on a virtual or artificialpotential field generated for each segment of that path to attract themanipulator to the path. The movement resulting from the calculatedpotential may then be projected onto the null-space for calculation ofnull-space coefficient to provide joint velocities that provide thedesired tracking movement. In cases where there is a network of paths,the resulting potential fields from the entire set of path segment (or aportion thereof) may be added together and may include some type ofweighting. Alternatively, the system may be configured to utilize onlythe potential field associated with the closest path segment. Theresulting motion provides that the null-space controller moves thejoints so that the manipulator arm traversed the specified network ofpaths to produce the desired movement of the joints within thenull-space, even during commanded end effector movement by the surgeon.

FIGS. 15-16 illustrate methods of reconfiguring a manipulator assemblyof a robotic surgical system in accordance with many embodiments of thepresent invention. FIG. 15 shows a simplified schematic of the requiredblocks need to implement the general algorithms to control the patientside cart joint states, in relation to the equations discussed above.According to the method of FIG. 15, the system: calculates the forwardkinematics of the manipulator arm; then calculates dx/dt using Equation(1), calculates dq_(perp)/dt using Equation (5), then calculatesdq_(null)/dt from z which may depend on dq_(perp)/dt and the Jacobianusing Equation (6). From the calculated dq_(perp)/dt and dq_(null)/dtthe system then calculates dq/dt and q using Equations (4) and (3),respectively, thereby providing the movement by which the controller caneffect the desired reconfiguration of the manipulator while maintainingthe desired state of the end effector and/or location of the remotecenter.

FIG. 16 shows a block diagram of an exemplary embodiment of the system.In response to a manipulation command, which commands a desired tool tipstate, a processor of the system determines the velocities of the tooltip and the states of the joints from which the dq_(perp)/dt iscalculated. To provide a desired path of joint movement for themanipulator arm, the system determined position-based constraints withinthe subspace of the joints for which controlled movement is desired,such as a network of paths. Optionally, the defined constraints may bealtered by a user input, such as a reconfiguration of one or more jointsdriven by a user or manually reconfigured in a clutch mode. Thedq_(null)/dt is then calculated so as to move the joints along thedefined network paths, such as through the use of an attractivepotential field for one or more segments of the network path which maybe added to the dq_(perp)/dt to calculate dq/dt so as to drive thejoint(s) of the system and effect the desired movement (or state) of theend effector while providing the desired movement of one or more jointswithin the null-space according to the desired movement.

FIGS. 17-18 illustrate methods of providing a desired movement of one ormore joints of a manipulator. The method of FIG. 17 includes:determining a set of position-based constraints within a joint spacethat correspond to a desired joint movement of one or more joints;determine a potential between the position of the one or more joints andthe constraints within an artificial potential field; calculating amovement of the manipulator arm within a null-space using the determinedpotential so that the one or more joints track the constraints; anddriving the joints according to the calculated movement to effect thedesired movement of the one or more joints, even concurrent with variousother movement of the joints. The method of FIG. 18 includes: providinga manipulator arm having a plurality of joints extending to a distal endeffector, the arm having a range of differing configurations for a givenend effector state; defining a set of position-based constraints thatcorrespond to a desired movement of one or more joints of the plurality;optionally, modifying the constraints based on a reconfigured positionof the one or more joints; determining a tracking movement of theplurality of joints within a null-space using a potential between theconstraints and a calculated position of the one or more joints; anddriving the joints according to the calculated movement to effect thedesired movement of the one or more joints, even concurrent with variousother movement of the joints.

While the exemplary embodiments have been described in some detail forclarity of understanding and by way of example, a variety ofadaptations, modifications, and changes will be obvious to those ofskill in the art. Hence, the scope of the present invention is limitedsolely by the appended claims.

What is claimed is:
 1. A method for a manipulator arm, the manipulatorarm comprising a movable distal portion that includes an end effector, aproximal portion coupled to a base, and a plurality of joints betweenthe distal portion and the base, the plurality of joints havingsufficient degrees of freedom to allow a range of differing joint statesfor a given state of the end effector, the method comprising: defining aposition-based constraint of one or more joints of the plurality ofjoints within a joint space of the plurality of joints, theposition-based constraint including one or more paths corresponding to adesired movement of the one or more joints within the joint space of theplurality of joints; receiving a manipulation command to move the endeffector with a desired end-effector movement; calculating anend-effector displacing movement of the plurality of joints to effectthe desired end-effector movement, wherein calculating the end-effectordisplacing movement of the plurality of joints comprises calculatingjoint velocities of the plurality of joints from directions thatcorrespond to the end effector moving; calculating a tracking movementof the plurality of joints so as to move a position of the one or morejoints of the plurality of joints towards the position-based constraint,wherein calculating the tracking movement of the plurality of jointscomprises calculating joint velocities of the plurality of joints fromdirections that correspond to the end effector not moving; and drivingthe plurality of joints according to the calculated movements so as toeffect the end-effector displacing movement concurrently with thetracking movement.
 2. The method of claim 1, further comprising:calculating values for a Jacobian of the manipulator arm, the jointvelocities from directions that correspond to the end effector notmoving being associated with a null space of the Jacobian, and the jointvelocities from directions that correspond to the end effector movingbeing associated with a null-perpendicular space of the Jacobian.
 3. Themethod of claim 1, wherein a first path of the one or more paths of theposition-based constraint has at least one dimension and is definedwithin a subspace of the joint space of the plurality of joints by atleast two joints of the plurality of joints.
 4. The method of claim 1,wherein the one or more paths of the position-based constraint include anetwork of piecewise continuous paths within the joint space of theplurality of joints.
 5. The method of claim 1, wherein calculating thetracking movement comprises: defining a potential field between acalculated position of the one or more joints of the plurality of jointsand the one or more paths of the position-based constraint, wherein anincreasing potential of the potential field corresponds to an increasingdistance between the calculated position and the one or more paths;determining from the potential field a potential between the calculatedposition and the one or more paths; and calculating the trackingmovement by using the potential to determine a direction from thecalculated position towards the one or more paths.
 6. The method ofclaim 1, wherein calculating the tracking movement comprises:determining a first movement of the plurality of joints within the jointspace of the plurality of joints by evaluating a potential function ofthe one or more joints of the position-based constraint; and determiningthe joint velocities of the plurality of joints for the trackingmovement by projecting the first movement of the plurality of jointsonto a null space of a Jacobian of the manipulator arm.
 7. The method ofclaim 1, wherein the distal portion of the manipulator arm includes aninstrument holder that releasably supports a surgical instrument havingan elongate shaft extending distally to the end effector, the shaftpivoting about a remote center of motion during surgery.
 8. A systemcomprising: a manipulator arm comprising a movable distal portion thatincludes an end effector, a proximal portion coupled to a base, and aplurality of joints between the distal portion and the base, theplurality of joints having sufficient degrees of freedom to allow arange of differing joint states for a given state of the end effector;an input device for receiving a manipulation command to move the endeffector with a desired end-effector movement; one or more processorsoperably connected to the input device and the manipulator arm, the oneor more processors being configured to perform operations including:defining a position-based constraint of one or more joints of theplurality of joints within a joint space of the plurality of joints, theposition-based constraint including one or more paths corresponding to adesired movement of the one or more joints within the joint space of theplurality of joints; calculating an end-effector displacing movement ofthe plurality of joints to effect the desired end-effector movement,wherein calculating the end-effector displacing movement of theplurality of joints comprises calculating joint velocities of theplurality of joints from directions that correspond to the end effectormoving; calculating a tracking movement of the plurality of joints so asto move a position of the one or more joints of the plurality of jointstowards the position-based constraint, wherein calculating the trackingmovement of the plurality of joints comprises calculating jointvelocities of the plurality of joints from directions that correspond tothe end effector not moving; and transmitting a command to themanipulator arm to drive the plurality of joints according to thecalculated movements so as to effect the end-effector displacingmovement concurrently with the tracking movement.
 9. The system of claim8, wherein the operations further comprise: calculating values for aJacobian of the manipulator arm, the joint velocities from directionsthat correspond to the end effector not moving being associated with anull space of the Jacobian, and the joint velocities from directionsthat correspond to the end effector moving being associated with anull-perpendicular space of the Jacobian.
 10. The system of claim 8,wherein a first path of the one or more paths of the position-basedconstraint has at least one dimension and is defined within a subspaceof the joint space of the plurality of joints by at least two joints ofthe plurality of joints.
 11. The system of claim 8, wherein the one ormore paths of the position-based constraint include a network ofpiecewise continuous paths within the joint space of the plurality ofjoints.
 12. The system of claim 8, wherein calculating the trackingmovement comprises: defining a potential field between a calculatedposition of the one or more joints of the plurality of joints and theone or more paths of the position-based constraint, wherein anincreasing potential of the potential field corresponds to an increasingdistance between the calculated position and the one or more paths;determining from the potential field a potential between the calculatedposition and the one or more paths; and calculating the trackingmovement by using the potential to determine a direction from thecalculated position towards the one or more paths.
 13. The system ofclaim 8, wherein calculating the tracking movement comprises:determining a first movement of the plurality of joints within the jointspace of the plurality of joints by evaluating a potential function ofthe one or more joints of the position-based constraint; and determiningthe joint velocities of the plurality of joints for the trackingmovement by projecting the first movement of the plurality of jointsonto a null space of a Jacobian of the manipulator arm.
 14. The systemof claim 8, wherein the distal portion of the manipulator arm includesan instrument holder that releasably supports a surgical instrumenthaving an elongate shaft extending distally to the end effector, theshaft pivoting about a remote center of motion during surgery.
 15. Anon-transitory readable memory storing a processor-implemented programfor moving a manipulator arm, the manipulator arm comprising a movabledistal portion that includes an end effector, a proximal portion coupledto a base, and a plurality of joints between the distal portion and thebase, the plurality of joints having sufficient degrees of freedom toallow a range of differing joint states for a given state of the endeffector, and the processor-implemented program including instructionsthat, when executed by one or more processors, cause the one or moreprocessors to perform operations comprising: accessing values thatdefine a position-based constraint of one or more joints of theplurality of joints within a joint space of the plurality of joints, theposition-based constraint including one or more paths corresponding to adesired movement of the one or more joints within the joint space of theplurality of joints; accessing values for a manipulation command to movethe end effector with a desired end-effector movement; calculating anend-effector displacing movement of the plurality of joints to effectthe desired end-effector movement, wherein calculating the end-effectordisplacing movement of the plurality of joints comprises calculatingjoint velocities of the plurality of joints from directions thatcorrespond to the end effector moving; calculating a tracking movementof the plurality of joints so as to move a position of the one or morejoints of the plurality of joints towards the position-based constraint,wherein calculating the tracking movement of the plurality of jointscomprises calculating joint velocities of the plurality of joints fromdirections that correspond to the end effector not moving; andtransmitting a command to the manipulator arm to drive the plurality ofjoints according to the calculated movements so as to effect theend-effector displacing movement concurrently with the trackingmovement.
 16. The readable memory of claim 15, wherein the operationsfurther comprise: calculating values for a Jacobian of the manipulatorarm, the joint velocities from directions that correspond to the endeffector not moving being associated with a null space of the Jacobian,and the joint velocities from directions that correspond to the endeffector moving being associated with a null-perpendicular space of theJacobian.
 17. The readable memory of claim 15, wherein a first path ofthe one or more paths of the position-based constraint has at least onedimension and is defined within a subspace of the joint space of theplurality of joints by at least two joints of the plurality of joints.18. The readable memory of claim 15, wherein the one or more paths ofthe position-based constraint include a network of piecewise continuouspaths within the joint space of the plurality of joints.
 19. Thereadable memory of claim 15, wherein calculating the tracking movementcomprises: defining a potential field between a calculated position ofthe one or more joints of the plurality of joints and the one or morepaths of the position-based constraint, wherein an increasing potentialof the potential field corresponds to an increasing distance between thecalculated position and the one or more paths; determining from thepotential field a potential between the calculated position and the oneor more paths; and calculating the tracking movement by using thepotential to determine a direction from the calculated position towardsthe one or more paths.
 20. The readable memory of claim 15, whereincalculating the tracking movement comprises: determining a firstmovement of the plurality of joints within the joint space of theplurality of joints by evaluating a potential function of the one ormore joints of the position-based constraint; and determining the jointvelocities of the plurality of joints for the tracking movement byprojecting the first movement of the plurality of joints onto a nullspace of a Jacobian of the manipulator arm.